Teleportation makes the question a lot weirder than the answers have implied. I mean, who knows how the teleportation works in the first place? Maybe it cancels momentum on its own (and the question seems to be about momentum rather than gravity itself, considering that he's asking what would happen if some already falling in air suddenly teleported into water). I think the answer depends entirely on how the teleportation works, and is therefore kind of meaningless without more context.

Incidentally, teleportation as it is often portrayed in fiction would probably violate some basic laws of physics because of potential energy.